Film-forming resinous lining for metal containers



Dec. 24, 1946. wARTH ET AL 2,413,093

FILM-FORMING RESINOUS LINING FOR METAL CONTAINERS Filed July 20, 1942' a Mam bow! Patented nee- 24, 1946 FILM-FCBMING RESINOUS LINING FOR CONTAINEBQ Albln n. warm and hiya F. Bulatkin, Baltimore, Md, assignors to Crown Cork & Seal Company, 1110., Baltimore, Md., a corporation of New York Application July 20, 1942, Serial No. 451,620

This invention relates to containers for maintaining the original quality and freshness of foods and beverages, particularly beer and ale.

A most significant feature of the present invention is the provision of a container having a lining which is stable to such delicate products as beers and ales, acid resistant and containing no metallic elements that might react with the proteins in such beers and ales. This container is provided with a wax coating superposed uponthe lining at the bottom seal onlyinstead of the ,usual overall wax coating. The wax coating at the seam is assurance against any possibility ofvrusting and also enhances the seal at the seam.

A container having a. construction of this character precludes the necessity of using aluminum coated steel and which moreover must have an overall coating of wax to prevent bleaching 'of the contents, such as beer by'the aluminum. In other words, the lining of the container of this invention does not exert this objectionable efiect and hence a wax coating for the entire container body as generally used is now obviated.

The primary object of the invention is to pro-- vide a container having a lining which is nonabsorbent as regards the contents. Thus, the

' principles contributing to the flavor, aroma and @4Clalms. (omen-s2) neck, and lip are drawn and formed from a single metal blank, e. g. black iron and are devoid of seams. The invention, however, is applicable to the lining of all types of containers, and in addition to metal cans, may be used upon paper receptacles as well as receptacles of plastics or synthetic materials.

heretofore been suggested, but it was found that such coatings tend to absorb the taste and flavor of beverages, such as beer, and are, therefore,

objectionable. Attempts have been made to overcome this deficiency in such coatings by adding flavor-imparting ingredients, such as lupilin, but such expedients have not been found to be satisfactory.

Linings iormed from synthetic resin varnish-' like materials have also been used, but have been found to be objectionable for various reasons.

. Our invention resides. in the discovery that "Aruba resin when incorporated in a lining having a. suitable non-volatile, film-forming vehicle In the drawing: Figure 1 is a side elevation partly broken away, showing our improved continuous lining applied to the container, and it is to be noted that the lining flows to such an extent as to cover a portion of the exposed surface of .the sealing lip at the mouth of the container upon which the cork cushion of a cap such as the crown cap rests when the same is crim-ped upon the container;

Figure 2 illustrates the manner of applying wax to the can bottom, and

Figure 3 illustrates the manner in which the wax drops are caused to flow into the bottom seam upon the lining so as to protect the seam against rusting; and fortify the seal.

The container shown in Figure 1 is formed of 7 sheet metal, such as black iron or steel, and is seamless, i. e., the body l0, top H, neck [2, and sealing lip or'cap receiving finish [3 are integral, being drawn from a single metal blank. The bottom I! is convex, as shown, and is secured to the body In by seaming in the usual manner, as

' other finishes may be used. if desired.

The lining 16 has the important characteristic of being non-absorbent and thereby preserves the original quality and freshness of the most delicate foods and beverages. Furthermore, it is inert to the black iron 01 the container and to the beverage or food contents. In this respect it is advantageous over metallic coatingsin which electrolytic action may take place, leading to corrosion as well as objectionable effects upon the contents. v

A composition suitable for a lining has for an essential constituent a black bituminous resin known as Aruba resin purchasable in the open market, and preferably having a. melting point of about 400 F. Aruba resin" isa natural bituminous resin imported from the island of Aruba in Curacao, Dutch West Indies. The Wilson Carbon Company, New York city, markets this resin under the name of "Vanadiset resin, the name being derived from the presence of a rare earth material in the resin, namely, approximately 0.25 percent of vanadium pentoxide (V205). The resin contains about 25 percent of fixed carbon and the total elemental canbon of about 84.4% is in a colloidal form, and several percent of sulfur, but less than 0.5 percent of mineralmatter. The resin is described by'the seller as a crystalline form, readily pulverized, product of petroleum butane distillation and as a. thermoplastic resin, which becomes plastic under treatment with heat. This Aruba resin is a black pitch contrasted to an asphalt which latter contains a. much higher fixed carbon content, the range being being 36 to 43 percent for Trinidad, Bermudez, Gilsonite, Tabylite, Wurtzilite, etc, (see Handbook of Chemical Engineering, vol. II, p. 647, by Liddell). The presence of 0.25 per- .cent of vanadium pentoxide in Aruba resin is of value as a deoxidizing agent in the preservation of the film flexibility of varnishes made therefrom. The color of "Aruba resin" or Vana- 'diset resin is jet black, but brown when dissolved, and it is obtainable in grades melting at about 300 F. and 400 F. This 400 F. melting point Aruba resin" is much higher than the melting points of the natural asphaltic resins, which in general melt below 300 F.

"Aruba resin is a thermoplastic hydrocarbon compound containing vanadium pentoxide. It is also refered to as Aruba bitumen and as Vanadiset resin as above explained. The name Vanadiset resin has superseded Aruba resin in some cases since it is more expressive of the fact that this peculiar resin contains vanadium,

which does not' occur in any other known bitumen, and is believed to give it ahigh tensile strength without the elongation common to other pitch materials. The ash content (mineral matter) is about 0.5 percent, and it therefore contains little inorganic impurity.

An analysis of "Aruba resin is as follows:

Percent Total carbon compounds 84.24

- Total fixed carbon 24.74 Hydrogen 8.53 Nitrogen 1.12 Ash content (mineral matter) 0.57 V205 0.25 Water 4.00

Molecular weight 3200 The average moisture content of "Vanadiset" resin is 5.70 percent (as shipped), volatile matter (dry basis) 74.24 percent, fixed carbon 25.35 g

percent, ash .41 percent, vanadium oxide in ash 48.00 percentpmelting point 300 F. to 400 F., specific gravity L117 at flash point SOD-635 F.

By way of illustration, a preferred example has the following formula:

Formula for black pitch coating Parts by weight Aruba resin 84.0 Rezyl resin #38'7-2 325.5 W. kerosene 205.5 Solvesso #3 120.0

Total 735.0

Rezyl resin #387-2 is a short oil soya bean alkyd resin in solvent of the American Cyanamid Co. Kerosene is water white. Solvesso #3 is 4 an aromatic hydrocarbon solvent of the Standard Oil of New Jersey. Rezyl resin #387-2 contains about 50 percent resin and 50 percent of Solvesso #3 orits equivalent.

The' 325-5 lbs. of #387-2 Rezyl resin is prefer- "ably mixed with the 120.0 lbs. of Solvesso #3 Aruba resin "pounds" 70 Rezyl resin #387-2 galions 38.8 Kerosene do 31.0 Solvesso #3 do 16.6

In a further example, this resin may be mixed with fullers earth or volcanic clay, such as bentonite, together with a suitable plasticlzer such.

as a reaction product between rosin and diethylene glycol or other plasticizer which, in its dry form, flows very sluggishly. The composition is carried in a solvent such as xylol or Solvesso" sold by Standard Oil Company of New Jersey and is sprayed upon the container or the plate from which it is to be made. Thereafter, the sprayed coating is baked during which step the solvent is driven off and the coating is caused to flow so as to cover the exposed lip portion 11, and a thin continuous lining is produced which is non-absorbent. Such a protective coating on black plate will not be easily fractured. The coating is baked at a temperature of about 400 F. to 425 F. or above for a period of twenty minutes or more, the temperature being at or above the melting point of the resin ingredient, and a hard, dry, firm but flexible coating is produced.

Another lining is prepared by using a mixture of Duraplex resin and Aruba resin. Duraplex resins are drying oil and non-drying oil alkyd resins, of which the products derived from phthalic anhydride, glycerine, and oil fatty acids may be considered the proto type. (This definition is taken from Duraplex bulletin of the Reslnous Products 8: Chemical Co., Inc., Philadelphia, Pa.) A suitable resin is Duraplex C-49-S, which is a long oil drying type alkyd resin for air drying and baking finishes.

Below is a formula for the "Aruba resin" pitch coating including Duraplex" resin:

Parts :by weight Aruba resin 300 Bentonite Duraplex C-49-S 450 Solvent 1500 In preparing the coating 150 parts of bentonite are placed in a ball mill with 150 parts of solvent, e. g., a high boiling naphtha. After several hours of rotating the "Aruba resin" is added with 300 parts of additional solvent, and the rotating is continued for about 24 hours when "Duraplex" resin is added, with the remaining solvent. The rotation is continued for a few hours before the'ball mill is emptied. The product is filtered and is ready for use as a spray. The composition should approximate 30 percent solids and 70 percent solvent. The preferred drying temperature on steel is between 400 F. and 425 F. for a time period of 20 minutes inside spray and 30 minutes outside spray.

of the finished lining. The coating is baked at 400 F. to 425 F. The wax being of lower density than the Anrba resin and other solids in the composition has a tendency to bloom on the surface after ibaking. The wax is a particularly desirable ingredient in association with the Aruba resin since it is a fiexifying agent for the lining film and is quite stable at the high baking temperatures, such as 400 F. or more. Moreover, the wax does not impart objectionable odors or taste in the baked sprayed coating andin addition to its stability at high baking temperature, also does not volatilize.

A further very emcient baked spray coating consists in preparing a mixture of plasticizing vehicle composed of bodied linseed oil 28 parts, manganese drier 2 parts, Piccolyte resin ,17 parts, carnauba wax 3 parts, and solvent, such as xylene, 50 parts. condensation polymer derived from B-pinene, which is in turn prepared fr 3m turpentine. this mixture there is added 1/z pounds of .Aruba.

resin to the gallon of vehicle and the resin and' mixture are ground together preferably in a ball mill. The bodied linseed oil constitutes a-plasticizing agent while the Piccolyte resin acts as a bonding agent and the camauba wax is pres.

Piccolyte resin is a chemical coatings particularly those used as spotting materials in caps. For instance, a suitable paper coated with one of these linings will form a center spot facing or an overall facing for the closure 6811 Also, closure caps such as crown caps I may be formed from sheet metal provided on one or both sides with one of the coatings described above. The lining as a coating is advantageous over many lacquers because of its non-scratchability, resistance to rust, pasteurization, sterilization, etc, when applied to plain clean steel. It is unnecessary to .bonderize, size,

or otherwise treat the steel before its .applica-' tion. We prefer to use somewhatmore 'resin and less solvent in the formula so as to body the material for coating instead of spray. It is also preferable to use a full pound or more of the Aruba resin to each gallon of vehicle.

prommately 38 percent of total solids and 62 per cent of solvent. The total solids contain resins suitably plasticized with drying oils, according to an analysis made of the product. Vehicles of a similar nature are obtainable on the market from numerous sources of su ply.

A satisfactory lining has been prepared from the black bituminous resin sold under the trade name Vanadiset. and the G-80 vehicle, by

grinding the resin in the vehicle preferably by Aruba does not have the objectionable flavor absorptive characteristics of gilsonite in the container lining art. It has, furthermore, been discovered that the Aruba," even when present in substantially lesser amounts than varnish forming vehicles, such as synthetic. resins, provides the characteristics desired and hereinbefore described.

While we have referred to the use of the compositions above mentioned as linings for metal containers, they are also satisfactory for paper 45. .container subjected to heating, the wax runs While the present container lining has great flowability so that it flows out 'upon the exposed surface ll of the lip of the container as well as into the joint defined by the seam [5 during baking, it is desirable to further fortify the bottom may be applied over the lining at any particular spot or section.

Generally, this improved waxing procedure consists in passing the containers on a conveyor belt under fixed pipettes not shown, which place a drop or drops of wax l8 on the surface of the center of the convex container bottom, as shown in Figure 2. Thereafter, the containers are heated as by passing onto a hot plate l9 or heated 3 section as shownin Figure 3, which melts or fur ther disperses the wax in case the container is cold. Preferably, the container is pre-heated before the introduction of the wax. After the wax has been dropped, as shown in Figure 2, and the over the convex irmer surface of the bottom and into the joint, filling the crevices thereof as shown at 20 in Figure 3.

The possibility of the rust condition developing, which condition does not always appear very pronounced in a beer package but can be easily detected by analytical methods, is reduced to a minimum and as will be noted, it is only necessary to utilize the wax in the lower joint of the container.

The amount of wax required is negligible and depends on the size of the container, in that about to %m% of a. gram will be satisfactory for a'12 fi. oz. container or about /6 of the 1.5 grams or more of wax required to completely coat the container.

As stated above, about 0.20 to 0.25 gram of wax are satisfactory and may be applied as a single drop or a plurality of drops, e. g., 3 drops, 6 drops,

opened and the wax is dropped at the maximum rate of 120 drops per minute, it takes 6 to 8 drops to secure a protective coating on theinside seam. This is equivalent to about .195 to .260 gram of wax. Minimum protection can be had with 3 drops, equivalent to .096 gram per can but a slightly greater amount is preferred. v

The drops of wax are dropped through the mouth of the can so that they fall upon the center of the inner convex surface as shown at I! in Figure 2. The wax can be permitted to drop upon a cold surface but it is preferred that the bottom be pre-heated since in the subsequent heating step, the flow of the wax is much greater. After receiving the drops of wax, the cold or preheated containers are subjected to heat on the bottom as shown in Figure 3 at a temperature of about 250 to 280 F. When the cans are cold it takes possibly 10 to seconds for the wax' to properly distribute itself around. a seam as shown at in Figure 3, but when the containers are first warmed the distribution time of the wax canbe substantially shortened to 5 to 10 seconds or less. The wax used has good flowing qualities and is one of those conventionally employed for container lining.

In applying the bituminous lining to the containers, the spraying is carried out with the containers upside down and with the bottom preferably attached, and the baking step is likewise conducted with the containers upside down. whereby sufiicient flow of the lining is assured to provide a thoroughly protective coating film on the exposed surface ll of the sealing lip continuous with the lining film on the interior wall and bottom of each container. When the wax-- ing stepis employed, the containers are in upright position and the wax dropped therein, as shown, upon the upwardly convex bottom.

The term .Aruba resin as set forth in the appended claims is intended to cover a product having the physical and chemical properties set forth herein.

We claim:

1. Ametal container having a lining in the form of a thin, continuous film comprising a major portion of film-forming resinous varnish having Aruba resin incorporated therein.

2. A metal container having a. lining in the form of a thin, continuous film comprising a major portion of film-forming resinous varnish having Aruba resin with a melting point between 300 F. and 400 F. incorporated therein.

3. A metal container having a lining in the form of thin, continuous film comprising a major portion of film-forming resinous varnish having incorporated therein Aruba resin and wax.

4. A metal container having a lining in the form of a thin, continuous film comprising a major portion of film-forming resinous varnish ha ing incorporated therein wax and Aruba resin having amelting point between 300 F. and

I ALBIN H. WARTH.

ILIYA F. BULATKIN. 

